(1) Field of the Invention
The present invention relates to an apparatus for detecting trace materials in a heterogenous sample. In particular, the present invention relates to an apparatus which separates trace evidence from a soil sample using jets of water and air bubbles which lift and separate the trace evidence from the soil and deposits the evidence on a fine mesh screen filter.
(2) Description of Related Art
The extraction of trace evidence materials from crime scene soil samples has remained a somewhat neglected area of research in forensic science. Trace evidence may be useful in event reconstruction and in determining the association of people, places, and things. Trace evidence of various forms (e.g. hairs, fibers, glass, and paint) may be associated with various soil materials. This mixture often results from crimes committed in various modes and environments. These methods are generally subjective, time consuming, and relatively inefficient. Furthermore, if trace evidence materials are obscured due to the adherence of soil particles they may be overlooked.
Conventional methods for the isolation of trace evidence from various substrates do exist; however, these techniques are generally limited to the processing of low volume dust samples (garments, and the like), and thus are not implemented specifically for high volume soil samples. The most common techniques implemented for the processing of soil for evidentiary purposes involve manual dry sieving and/or vacuuming, accompanied by visual microscopic observation and forceps removal. The prior art suggests that "hand" picking, which involves the observation and subsequent removal of trace evidence material from various substrates (garments, carpet, dust samples) with forceps, needles or magnets, is the best method of evidence collection (Gaudette, B. D., Forensic Science Handbook 2;209-272 (1988); Palenik, S., Forensic Science Handbook, 2:161-202, Englewood Cliffs, N.J.: Prentice Hall (1988); Saferstein, R., Criminalistics: An Introduction to Forensic Science (5th ed.). Englewood Cliffs, N.J.: Prentice Hall (1995) and Suzuki, E. A., Forensic Science Handbook, 3:24-70, Englewood Cliffs, N.J.: Prentice Hall (1993) suggest that following this initial examination, the material should then be observed under a stereo- binocular microscope, followed by forceps removal of evidentiary items. These methods, however, are extremely tedious, time consuming, and subject to human error, especially in instances of mass disaster and cremation for which trace evidence may be combined with large volumes of soil. Others suggest that trace evidence materials be collected via vacuuming, tape-lifting, shaking, or scraping, followed by microscopic examination and separation of evidence with forceps removal (Bisbing, R. E., Forensic Science Handbook 1:184-221 (1982); Osterberg, J. W., and R. H. Ward, Criminal Investigation: A Method for Reconstructing the Past (5th ed.). Cincinnati, Ohio: Anderson Publishing Co. (1992); Palenik, S., Forensic Science Handbook 2:161-202 (1998); Suzuki, E. A., Forensic Science Handbook 3:24-70 (1993)). However, these methods do not apply generally and are not commonly used for evidence extraction from soil samples alone. Thus, there is a need for a more quantitative and efficient technique.
A hydropneumatic elutriation apparatus has been utilized to extract root materials and other organic soil material from soil samples (U.S. Pat. No. 4,478,710 (1984) to Smucker et al; Smucker, A. J. M., Soil environmental modifications of root dynamics and measurement. Annual Review of Phytopathology 31:191-216 (1993); Smucker, A. J. M., et al., Agronomy Journal 74:500-503 (1982)). This apparatus separates materials based on differential density elutriation and has proven to be an efficient quantitative method of root system isolation. Used in conjunction with computer imaging, hydropneumatic elutriation allows precise quantitation of root system components (Smucker, A. J. M., Soil environmental modifications of root dynamics and measurement. Annual Review of Phytopathology 31:191-216 (1993)). An apparatus consisting of a battery of eight elutriation columns is commercially available for separating root materials from mineral soils. It was recognized in the patent disclosure that a comparable method could be utilized for the separation of trace evidence materials from soil samples; however, the apparatus was not designed to examine large volumes of soil for the purpose of using materials as evidence.
Other related prior art is set forth in U.S. Pat. No. 4,822,493 to Barbery, et al; U.S. Pat. No. 5,191,982 to Tong; U.S. Pat. No. 5,305,888 to Meylor et al; U.S. Pat. No. 5,307,937 to Hutwelker; U.S. Pat. No. 5,436,384 to Grant et al; and U.S. Pat. No. 5,458,738 to Chamblee et al.
There is a need for a trace evidence separation technique which would allow analysts to process numerous soil samples from a crime scene and quantitatively recover uncontaminated trace evidence from large sample volumes more effectively. Such a method could be successfully implemented and tremendously useful at crime scenes and in situations involving victim burial, explosions, cremations, and mass disasters in which trace evidence items are often combined with very large volumes of surface and/or deeper soil material.